1) Field of the Invention
The present invention is directed to tetraazapentalenes and methods of making tetraazapentalenes.
2) Description of Prior Art
One type of tetraazapentalene, dibenzotetraazapentalene, has a chemical structure of the form (Drawing 1):

Additionally, there are isomeric forms of dibenzotetraazapentalenes. One isomeric form has the following structure (Drawing 2):

There are also other tetraazapentalene structures that contain only one benzene ring or no benzene rings.
Many tetraazapentalenes have two benzenoid rings. These benzenoid rings, which are located on the far left and far right of the illustrated chemical structure, can be substituted or unsubstituted. Each benzenoid ring has six carbon atoms; and there are four replaceable hydrogens associated with the carbon atoms on each benzenoid ring. With two rings, there are a total of eight positions in the tetraazapentalene structure that can be substituted. In addition, the carbon atoms themselves in each benzenoid ring can be substituted. The types and locations of these substitutions determine the characteristics of the resultant tetraazapentalene. Two known species of tetraazapentalene are tetranitro dibenzo tetraazapentalene (“TACOT”) and tetranitro bipyrimidine tetraazapentalene (“TNBP”).
TACOT is a tetranitro tetraazapentalene where four of the replaceable hydrogens are substituted with nitro groups (NO2), and the four remaining replaceable hydrogens are unsubstituted. This results in the following structure (Drawing 3):

TNBP, is a tetranitro tetraazapentalene wherein the four remaining replaceable hydrogen groups in TACOT and the carbons atoms associated with those hydrogen groups are substituted with nitrogen atoms. TNBP has the following structure (Drawing 4):

U.S. Pat. No. 3,166,567 (“the '567 patent”) is directed to dibenzotetraazapentalenes, which are organic nitrogen containing cyclic compounds. Of particular note is the tetraazapentalene known as tetranitro dibenzo tetraazapentalene, which is a type of TACOT. The '567 patent lists the potential substituents nitro, halo, azido, amino and sulfonyl. For example, tetranitro dibenzo tetraazapentalenes, dichloro dibenzo tetraazapentalenes, diamino dibenzo tetraazapentalenes and diazidodinitro dibenzo tetraazapentalenes are discussed.
In Technical Report No. 47 by the Office of Naval Research and titled “Luminescent Nitro Derivatives of 5,11-Dehydro-5H,11H-benzotriazolo[2,1-a]benzotriazole”, tetraazapentalenes are disclosed that have the following structure (Drawing 5):
A variety of potential substituents for the Z, Y, W and X positions are provided. These substituents include nitro, amino and methyl groups. When Z=Y═W=X═NO2, a tetranitro tetraazapentalene is formed.
U.S. Pat. No. 4,340,430 (“the '430 patent”) is directed to a process for the production of azo, which is an intermediate found in the production of tetraazapentalene. According to the '430 patent, an amine, which could be nitroaniline, is coupled with 2,4,6-triaminopyrimidine. Sodium nitrite in an aqueous-mineral acid medium is used for diazotization of aminobenzenesulfonic or aminobenzenecarboxylic acid. In the disclosed method, 48 parts of 2-nitroaniline-4-sulfonic acid are dissolved in 750 parts by volume of water with 50 parts 30% sodium hydroxide. After filtration with 1 part of decolourising carbon, 110 parts of 30% hydrochloric acid are rapidly stirred into the clear solution. The suspension thereby obtained is cooled to 0° C., and 50 parts by volume of 4N sodium nitrite solution is introduced at 0° to 5° C. over the course of 15 minutes. The diazotization is complete after 15 minutes.
Excess nitrous acid is destroyed with urea or sulfamic acid, and the diazo suspension is adjusted to a pH of 4 to 4.5 with sodium acetate. A solution of 25 parts 2,4,6-triaminopyrimidine-1,3 in 600 parts by volume of water is added to the diazo suspension over the course of 1 hour. The temperature of the reaction mixture rises to 15° to 20° C. Stirring is continued until the coupling is complete, and the coupling mixture is then warmed to 40° to 45° C. over the course of 1 hour. The coupling mixture is then filtered. The filter cake is washed with water until it is as salt-free as possible.
Suspended in 260 parts by volume of water is 44 parts of the filter residue (16.5% aqueous paste corresponding to 7.2 parts of dry azo dyestuff sulfonic acid). After heating to 70° to 75° C., the suspension is adjusted to a pH of about 10 using 25% NH4OH. A solution of 2 parts of magnesium chloride hexahydrate in 30 parts of water is added. After stirring for 10 hours at 90° to 95° C., the pigment suspension is filtered hot, and the filter cake is washed with hot water until no more chlorine ions can be detected in the filtrate. The filter cake is then dried in vacuo at 100° C.
Although TACOT has been widely used as an explosive, explosives that can produce equivalent or increased explosions in a given amount of material are desired. For example, tetraazapentalenes having increased explosive capability and greater energy per unit of material are desired. These tetraazapentalenes would also exhibit greater stability at high temperatures.